Can you hang your laundry on the other side of the garden? Death sentence seems rather severe for droppings. Not sure I'd want to eat city pidgeon, god knows what they pick up! Not sure if this is true, but I've heard that the pidgeons with deformed feet are poison survivors (presumably the offspring of the poisoned bird), so you could possibly be ingesting it, as it would imply that there are birds about which have eaten poison and survived.